Study: Slow slide toward dementia offers time for prevention

More than two decades ago, Dr. Barry Reisberg identified what we now call mild cognitive impairment — memory and judgment problems that may be irritating but not disruptive. People with MCI may complain of forgetting familiar names, for example, or they may start having trouble managing family finances, or following a recipe. One study found that people diagnosed with MCI have greater difficulty playing FreeCell, a popular computer card game. • Big deal, people thought at first. Everyone seems to develop mild memory problems as they get older. Therefore, MCI must be a sign of normal aging. • Then scientists noticed that people diagnosed with MCI progressed to Alzheimer's disease faster than average.

Now Reisberg, clinical director at New York University's Alzheimer's Disease Center, has found that people who have what he calls subjective cognitive impairment — described as a vague sense that they can't remember as well as they used to — tend to progress to MCI faster than average.

Reisberg tracked 213 adults, whose mean age was 67.2 years, for an average of about seven years. At the start of the study he asked each one the question, "Do you have memory complaints?" More than half of those who answered "yes" progressed to MCI during the seven-year observation period, while only 15 percent of those who claimed to have no memory complaints developed MCI, and they took longer to develop measurable impairment.

Reisberg also found that people with SCI displayed a striking decrease in brain metabolism, especially in the memory area. People with Alzheimer's display the same decline.

These findings add to the evidence suggesting that Alzheimer's is not a distinct disease like cancer, but rather a slowly developing condition like heart disease, which takes a long time — usually decades — to develop.

"SCI begins 15 years before MCI," Reisberg says, "and MCI lasts about seven years before the onset of mild dementia, so we're talking about 22 years before (the onset of) Alzheimer's disease."

This is good news, in his opinion, because it provides time to take preventive action.

"If we can address the problem much earlier, maybe we can change the trajectory of the disease," Reisberg says.

Just as with heart disease, some people may possess genes that confer protection against dementia. A study just released found that people who carry a form of a gene that boosts levels of HDL, the "good" cholesterol, are far less likely to develop dementia. (A previous study found that such people also are far more likely to live to 100.)

And Reisberg contends that anything that helps your heart, such as exercise, optimal cholesterol levels and a healthy diet, will probably help your brain too.

"A heart-healthy life would be useful in terms of preventing Alzheimer's disease because vascular factors seem to be involved in evolution of dementia," he says.

As though underscoring that advice, a study just published in the Archives of Neurology found that moderate physical activity begun in midlife or even later reduces the risk of developing MCI, while a six-month high-intensity aerobic exercise program actually improves cognitive function in people who already have discernible cognitive impairment.

Another study reported in the same issue found that of the 1,324 people involved in the Mayo Clinic Study of Aging, those who engaged in moderate exercise, such as brisk walking, aerobics, swimming and strength training, reduced their risk of developing MCI by 39 percent. Even in late life moderate exercise reduced risk by 32 percent.

So in a sense, your brain is in your hands. You can't control the genes you inherited from your parents, but you can make choices that reduce your chances of developing dementia. And new drugs in development are expected to help prevent Alzheimer's in the same way that statins such as Lipitor and Crestor help prevent heart attacks and strokes.

As the authors of the Mayo Clinic study observed, good choices involve more than just diet and exercise.

"A subject who engages in regular physical exercise may also show the same type of discipline in dietary habits, accident prevention, adherence to preventive intervention, compliance with medical care and similar health-promoting behaviors," the authors state.

In other words, if you live well, you may live long too, and at least postpone the onset of dementia or Alzheimer's disease.

Tom Valeo writes frequently about health matters. He welcomes reader mail but cannot respond to individual queries. You may write him at tom.valeo@gmail.com.